5-Week Introductory Heat Training Plan

by the CORE Team

This plan is for athletes new to heat training. Following it will get you heat adapted within 5 weeks. You’ll be prepared to perform well in a hot climate, and you can add 2–3 more weeks to reach your full potential.

In summary:

Week 1: You’ll get warm during the last 15 minutes of 4 workouts.
Week 2: The warm part of 3 workouts will grow from 20 minutes to 30 minutes.
Week 3: You’ll do 3 heat sessions, where you’re in a heat training zone for 30–40 minutes each time.
Week 4: Another 3 heat sessions, extending the hot portion to 40–50 minutes each time. This may actually feel easier than Week 3, as your body is adapting.
Week 5: A repeat of Week 4. You’ll boost your adaptation further, and the sessions may feel easier than Week 4.

Before starting the plan, we recommend reading these brief articles:

Baseline fitness

Before starting this plan, athletes should be training at least 4 days/week for a minimum of 4 hours/week. They should be able to complete a workout of 60–75 minutes. To integrate this into our normal training plan, see the tips in Integrating Heat Sessions into Your Training Plan.

In addition, please read the article Heat Safety before starting the plan. It may also help to read the article How to do a Heat Session.

Week 1: Getting warm

Goal: Start to adjust the mind and the body to heat. Your Heat Adaption Score will likely not rise during this week, but you’ll become accustomed to the warmer skin temperatures that come with heat training. This week is important preparation!
Tip: Measure your sweat rate, and hydrate accordingly during/after the workout.

Monday: Elevating skin temperature

Start a normal indoor workout, wearing your normal clothing, and using fans if that’s typical.
Monitor core temp, skin temp, and Heat Strain Index on the CORE app.
For the last 15 minutes of the workout, turn off fans. If you don’t normally use fans (or the room temp is less than 18°C /64°F), add an extra layer of clothes to your torso.
- Monitor your CORE data, paying particular attention to skin temp. It should rise above 33.5°C/92°F by the end of the 15’, and you should be sweating fairly heavily.
- You’ll likely need to decrease power/pace to avoid a spike in heart rate.
- Your Heat Strain Index may reach 1–2, but you should not expect to accumulate a Heat Training Load.

Tuesday: Dialing in skin temperature

Like on Monday, turn off fans and/or add clothing for the last 15’ of the workout. Add enough clothes so that your skin temp is at least 34.0°C /93°F by the end of the 15’.

Thursday: Progressively warmer

Again, turn off fans and/or add clothing for the last 15’of the workout.
Your skin temperature target for today is 34.5°C /94°F by the end of the 15’.

Friday: Now the sweat is pouring

As usual turn off fans and/or add clothing for the last 15’.
Try to reach a skin temperature of 35.0°C /95°F by the end of the 15’.

Week 2: Beginning of heat training

Goal: Dial-in your heat setup and start to become more comfortable in the heat. Your Heat Adaption Score will rise only a few percentage points, but you’ll be prepared for longer and hotter sessions next week.

Tip: Measure your sweat rate, and hydrate accordingly during/after the workout.

Monday: Add heat at the end

Start your normal indoor workout, wearing light clothes and using fans to stay cool.
With 20 minutes left in the session, turn off fans and add two layers to your torso – perhaps a wind/rain jacket (to trap sweat) and a thermal layer on top of that. Also, wear long pants.
- Pay attention to your core temp, skin temp, and Heat Strain Index. Also monitor your heart rate.
- You’ll likely need to decrease power/pace, even though heart rate will stay quite elevated.
- Skin temp will quickly rise, and your Heat Strain Index should reach 3–4 by the end of the 20’.
- In that 20’, you may accumulate a Heat Training Load of 1–2.
After the session, remain overdressed for another 10’, while observing core temp, skin temp, and Heat Strain Index.

Wednesday: A little bit longer

Repeat Monday’s session, but do the last 25’ of the workout with heat.
Regulate exertion and clothing so that your Heat Strain Index is between 3–5 by the end of the workout.
You may reach a Heat Training Load of around 2.

Friday: A little longer and a little hotter

Repeat Wednesday’s workout, but do the last 30’ of the workout with heat.
Start the heat portion with a core temp of at least 38.0°C /100.4°F (if you’re having trouble reaching that core temp, try working harder to produce more heat).
Reach a HSI of 3–5 within 5 minutes of starting the heat portion, and keep it there for the rest of the workout.
You may reach a Heat Training Load of 3–4.

Week 3: Bring on the heat!

Goal: Do three moderately-intense heat sessions. By the end of this week, your Heat Adaptation Score should be around 25%, the threshold for ‘Heat Accustomed’.
Tip: Measure your sweat rate, and hydrate accordingly during/after the workout.

Monday. Start with intensity, switch to heat

Start an indoor workout, wearing light clothes and using fans to stay cool.
The first 30 minutes should be fairly intense – intervals at threshold or higher power/pace (heart rate zone 4 or 5). This should bring your core temp close to 38.5°C /101.3°F.
After 30 minutes, turn off fans, add multiple layers to your torso and wear long pants. A CORE heat suit is an alternative.
Regulate intensity to maintain a HSI of 3–5. Stay in heart rate zone 2–3 by decreasing power/pace.
Maintain a HSI of 3–5 for 30 minutes, then end the workout.
After the workout, keep wearing the extra clothes until your HSI drops below 2.
Goal is to accumulate a Heat Training Load of 4–6.

Wednesday. Start warm, get hotter

Plan on a 60-minute workout. Start by wearing your ‘heat clothes’, with no fans.
Maintain a moderate exertion level – heart rate zone 2. If, after 20 minutes your Heat Strain Index is below 2, increase exertion to heart rate zone 3 for 10 minutes.
For the rest of the workout, maintain a Heat Strain Index of 3–5. Regulate exertion and clothing as needed.
End the workout once you’ve accumulated a Heat Training Load of 4.
After the workout, keep wearing the extra clothes until your HSI returns to below 2. You'll likely accumulate another HTL point.

Friday: Athlete’s choice

Repeat either Monday’s or Wednesday’s workout – your choice.
End the workout once you’ve accumulated a Heat Training Load of 5.
After the workout, keep wearing the extra clothes until your HSI returns to below 2.

Week 4: Now you’re hot!

Goal: Do three intense heat sessions. By the end of this week, your Heat Adaptation Score should be around 50%, the threshold for ‘Heat Adapted’.
Tip: Measure your sweat rate, and hydrate accordingly during/after the workout.

Monday: Athlete’s choice

Choose one of the workouts from Week 3.
Maintain a HSI of 4–6 for 40–50 minutes.
End the workout once you’ve accumulated a Heat Training Load of 5.
After the workout, keep wearing the extra clothes until your HSI returns to below 2. You'll likely accumulate another HTL point.

Wednesday: Athlete’s choice.

As described in Monday’s workout.

Friday: Athlete’s choice.

As described in Monday’s workout.

Week 5: Heat adapted

Goal: Do three intense heat sessions. By the end of this week, your Heat Adaptation Score should be between 60–75%, well into the ‘Heat Adapted’ range. At this level, you could expect to compete in hot conditions with little performance loss.
Tip: Measure your sweat rate, and hydrate accordingly during/after the workout.

Repeat Week 4 sessions

Do the same 3 sessions you did in Week 4, Monday, Wednesday and Friday.
Pay attention to all relevant metrics:
- Heat Strain Index
- Power/pace
- Heart rate
Indication of heat adaptation.
- You have to work harder (or dress warmer) to raise your HSI to the same values as prior weeks.
- Your heart rate is lower for a given power/pace
- You can maintain a given power/pace longer, even when your HSI is elevated
- Your sweat rate has increased from week 1.

Beyond Week 5: Maintain or adapt further

Goal: Do you want to maintain your heat adaptation, or adapt even further? Do you want to become a Heat Champion and make gains in hemoglobin and VO2max?

Heat Maintenance

To maintain your Heat Adaptation Score, do 2–3 heat sessions a week, accumulating a total Heat Training Load of approximately 12 for each week. Either 3 sessions of HTL 4, or 2 sessions of HTL 6 should be sufficient.

Adapting further

Repeating the Week 4 sessions should earn you Heat Champion status within 2–3 weeks. Add a fourth session each week if you want to get there quicker.

Heat Champion

Maintaining the Heat Champion for 3 weeks should increase your hemoglobin mass and likely your VO2max – each by 3–6%. This should increase your performance in both hot and cool conditions.